Die structure, transfer molding apparatus, transfer molding method, optical member, area light source device, liquid crystal display device, and mobile device

ABSTRACT

A transfer molding method includes an insertion step of inserting a resin sheet between a first die and a second die, which are disposed opposite each other, a sandwiching step of sandwiching the resin sheet between the first and second dies while a transfer surface of a transfer member is brought into contact with at least one of surfaces of the resin sheet, and a transfer molding step of heating at least one of the first and second dies to melt at least a surface portion of the resin sheet with which the transfer surface of the transfer member is brought into contact, and exhausting residual air remaining in a recess through a groove portion connected to the recess when a thick portion is formed by the recess formed in the transfer surface.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent ApplicationNo. 2012-243980, filed on Nov. 5, 2012, the subject matter of which ishereby incorporated by reference.

BACKGROUND

1. Technical Field

The present invention relates to a transfer-molding die structure, atransfer molding apparatus, a transfer molding method, an opticalmember, an area light source device, a liquid crystal display device,and a mobile device.

2. Related Art

Conventionally, for example, Japanese Unexamined Patent Publication No.2005-310286 discloses a transfer-molding die structure, which isincorporated in an optical-product transfer molding apparatus. Theoptical-product transfer molding apparatus heats and pressurizes a resinfilm between a first die and a second die using a transfer plate toperform the transfer molding of a finely irregular pattern. Theoptical-product transfer molding apparatus includes: the transfer platethat includes a transfer surface used to perform the transfer molding toa transferred portion of the resin film; an elastic plate that presses aperipheral portion located around the transferred portion of the resinfilm; and a transfer-plate heating mechanism and a transfer-platecooling mechanism, which are provided in at least one of the first dieand the second die.

However, in the conventional die structure, it takes a long time toremove a bubble generated in the transfer molding. Particularly, in thecase that a projecting portion is formed in the surface of the resinsheet, a large amount of air remains in a recess, which is provided inthe transfer plate (a transfer member) in order to form the projectingportion, and it takes a longer time to remove a residual air, whichdegrades productivity.

As illustrated in FIG. 8A, in the case that plural arc regions (a bolddotted line) including tapered surfaces are continuously arrayed in aninner edge portion of the recess of the transfer member, a flow rate ofa molten resin is not homogenized. Therefore, a region of fast flow rateof the molten resin differs from a region of slow flow rate of themolten resin in a deformation amount of the residual air (a bold solidline), and the residual air is deformed from an even width to differentshapes (FIGS. 8B to 8E). As a result, as illustrated in FIG. 8F, aboundary bubble that is generated by separating part of the residual airremains in a molding product to degrade a yield ratio.

SUMMARY

One or more embodiments of the present invention provides a diestructure, a transfer molding apparatus, and a transfer molding method,in which the residual air generated during the transfer molding cansurely and rapidly removed, and an optical member, an area light sourcedevice, a liquid crystal display device, and a mobile device, which areproduced by the transfer molding method. A light guide plate and a prismsheet can be cited as an example of the optical member.

In accordance with one or more embodiments of the present invention, adie structure includes: a first die; a second die that can relatively beseparated from and brought into contact with the first die; and atransfer member that is provided in at least one of the first and seconddies, the transfer member performing transfer molding while bringing atransfer surface into contact with a resin sheet supplied between thefirst and second dies, wherein the transfer member includes a recessthat is formed in the transfer surface and at least one groove portionthat is connected to the recess.

Accordingly, the residual air, which is generated when the transfersurface of the transfer member is brought into contact with the resinsheet to perform the transfer molding, can surely and rapidly beexhausted through the groove portion.

The groove portion may have a shape in which the groove portion isdirectly connected to the recess. The groove portion may be connected tothe outside, or not connected to the outside. There is no practicalissue when a portion molded in the groove portion is removed in grindingwork after the molding.

In the die structure in accordance with one or more embodiments of thepresent invention, the groove portion may have a depth greater than orequal to that of the recess.

Accordingly, the residual air is hardly trapped in the inner surface ofthe recess, and the residual air can surely and rapidly be exhaustedthrough the groove portion.

In the die structure in accordance with one or more embodiments of thepresent invention, the groove portion may be connected to an outside ofthe transfer member.

Accordingly, the residual air can further surely and rapidly beexhausted to the outside.

In the die structure in accordance with one or more embodiments of thepresent invention, the groove portion may be formed to intersect therecess formed in the transfer surface.

Accordingly, a degree of freedom of design of the groove portion isincreased to facilitate the design.

In the die structure in accordance with one or more embodiments of thepresent invention, the transfer member may include an auxiliary grooveportion that is formed to be connected to the recess, and the grooveportion may be connected to the recess through the auxiliary grooveportion.

Accordingly, the residual air temporarily collected in the auxiliarygroove portion is surely and rapidly exhausted through the grooveportion, so that the residual air can further surely and rapidly beexhausted.

In the die structure in accordance with one or more embodiments of thepresent invention, each groove portion may have a sectional area of afolding-fan-shaped flow path in which a pressure of a molten resinflowing from the recess is substantially equalized.

Accordingly, the residual air is equally exhausted from each grooveportion, the residual air can further rapidly be exhausted.

In the die structure in accordance with one or more embodiments of thepresent invention, each groove portion may be disposed in a positionwhere a flow rate of the molten resin is substantially equalized.

Accordingly, the flow of the molten resin is homogenized tosimultaneously and evenly exhaust the residual air, so that productivitycan be improved.

In accordance with one or more embodiments of the present invention, atransfer molding apparatus includes the die structure described above.

Accordingly, one or more embodiments of the present invention providesthe transfer molding apparatus in which the residual air, which isgenerated when the transfer surface of the transfer member is broughtinto contact with the resin sheet to perform the transfer molding, cansurely and rapidly be exhausted through the groove portion.

In accordance with one or more embodiments of the present invention, atransfer molding method includes: an insertion step of inserting a resinsheet between a first die and a second die, which are disposed oppositeeach other; a sandwiching step of sandwiching the resin sheet betweenthe first and second dies while a transfer surface of a transfer memberis brought into contact with at least one of surfaces of the resinsheet; and a transfer molding step of heating at least one of the firstand second dies to melt at least a surface portion of the resin sheetwith which the transfer surface of the transfer member is brought intocontact, and exhausting residual air remaining in a recess through agroove portion connected to the recess when a thick portion is formed bythe recess formed in the transfer surface.

Accordingly, one or more embodiments of the present invention providesthe residual air, which is generated when the transfer surface of thetransfer member is brought into contact with the resin sheet to performthe transfer molding, can surely and rapidly be exhausted through thegroove portion.

In the transfer molding method in accordance with one or moreembodiments of the present invention, the groove portion may have adepth greater than or equal to that of the recess.

Accordingly, the residual air is hardly trapped by the inner surface ofthe recess, and the transfer molding method in which the residual aircan surely and rapidly be exhausted through the groove portion isobtained.

In the transfer molding method in accordance with one or moreembodiments of the present invention, a molten resin may be caused toflow partially to the groove portion in which a nonproductive portion ismolded in the transfer molding step.

Accordingly, the residual air can surely be exhausted to improve theyield ratio. There is no practical problem when the nonproductiveportion is removed in the grinding work after the molding.

In accordance with one or more embodiments of the present invention, anoptical member is molded by the above transfer molding method.

Accordingly, the residual air can surely and rapidly be exhausted, andthe high-productivity, good-yield-ratio optical member is obtained.

In accordance with one or more embodiments of the present invention, anarea light source device includes: the optical member in accordance withone or more embodiments of the present invention; and a light sourcethat is disposed in at least one end face of the optical member, whereinlight incident from the light source to the optical member is outputthrough a light exit surface of the optical member.

Accordingly, the residual air can surely and rapidly be exhausted, andthe high-productivity, good-yield-ratio area light source device isobtained.

In accordance with one or more embodiments of the present invention, aliquid crystal display device includes: the area light source device inaccordance with one or more embodiments of the present invention; and aliquid crystal panel.

Accordingly, the residual air can surely and rapidly be exhausted, andthe high-productivity, good-yield-ratio liquid crystal display device isobtained.

In accordance with one or more embodiments of the present invention, amobile device includes the area light source device in accordance withone or more embodiments of the present invention.

Accordingly, the residual air can surely and rapidly be exhausted, andthe high-productivity, good-yield-ratio mobile device is obtained.

According to one or more embodiments of the present invention,advantageously the residual air, which is generated during the transfermolding in which the transfer surface of the transfer member istransferred to the resin sheet, can surely and rapidly be removed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating an optical member formingapparatus according to one or more embodiments of the present invention;

FIG. 2 is a partially one or more exploded perspective viewschematically illustrating a transfer molding apparatus in FIG. 1;

FIG. 3A is a partial bottom view of an upper-die transfer plate in FIG.2, FIG. 3B is a partially schematic sectional view of a die portion inFIG. 2, and FIG. 3C is a partially enlarged sectional view of the dieportion in FIG. 2;

FIGS. 4A and 4B are partial plan views illustrating first and secondmodifications of one or more of the embodiments;

FIGS. 5A, 5B, 5C, and 5D are partial plan views illustrating third,fourth, fifth, and sixth modifications of one or more of theembodiments;

FIGS. 6A and 6B are a graph and an evaluation table illustrating ananalysis result, which is performed to obtain an optimum slit widthdimension removing a residual bubble;

FIGS. 7A and 7B illustrate a measurement position and a graph of ameasurement result when a flow rate of a molten resin changed dependingon existence or non-existence of a slit is measured;

FIG. 8 is a view illustrating a flow rate of the molten resin in one ormore of the embodiments, FIG. 8A is a partially enlarged view of theflow rate of the molten resin, and FIGS. 8B, 8C, 8D, 8E, and 8F areschematic diagrams illustrating deformation and split processes of along and thin residual air;

FIG. 9A is an explanatory view illustrating a positional relationshipbetween a half-finished plate and a cutting tool, and FIG. 9B is asectional view illustrating a state in which a half-finished product iscut, and FIG. 9C is a sectional view illustrating a state immediatelyafter the half-finished product is cut; and

FIG. 10 is a sectional view illustrating a liquid crystal display devicein which a light guide plate and a prism sheet, which are opticalmembers of one or more of the embodiments, is incorporated.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present invention will be described withreference to the accompanying drawings. In the following description, aterm indicating a specific direction or position (for example, a termincluding “upper”, “lower”, “side”, and “end”) is used. The term is usedin the drawings only for the purpose of easy understanding of thepresent invention, but the technical scope of the present invention isnot limited to the term. The following description is made only by wayof example, but the present invention and application of the presentinvention are not limited to the following description. In embodimentsof the invention, numerous specific details are set forth in order toprovide a more thorough understanding of the invention. However, it willbe apparent to one of ordinary skill in the art that the invention maybe practiced without these specific details. In other instances,well-known features have not been described in detail to avoid obscuringthe invention.

(Configuration)

FIG. 1 illustrates a schematic optical member forming apparatusaccording to one or more embodiments of the present invention. Theoptical member forming apparatus includes a material supply apparatus 1,a transfer molding apparatus 2, a film adhesion apparatus 3, a cuttingapparatus 4, and an outline machining apparatus 5.

The material supply apparatus 1 rewinds a resin sheet 25 wound around amain roller 6, and supplies the resin sheet 25 to the transfer moldingapparatus 2. Plural rollers 7 are disposed in the material supplyapparatus 1, a protective sheet adhering to the resin sheet 25 is peeledoff immediately after the second roller 7, and the protective sheet iswound by a winding roller 8. At this point, the resin sheet 25 is madeof polycarbonate (melting points of 220 to 230° C., and aglass-transition temperature of about 150° C.).

As illustrated in FIG. 2, the transfer molding apparatus 2 includes alower die 9 and an upper die 10.

In the lower die 9, a lower-die intermediate plate 12, a lower-dieheat-insulating plate 13, and a lower-die transfer plate 14 aresequentially disposed on an upper surface of a lower-die support plate11.

The lower-die support plate 11 made of stainless steel (SUS) is formedinto a rectangular plate shape when viewed from above. Pluralthrough-holes are made between side surfaces of the lower-die supportplate 11, and heaters 15 and thermocouples (not illustrated) areinserted in the through-holes. The lower-die support plate 11 is heatedby energizing the heaters 15, and a temperature at the lower-dietransfer plate 14 can be raised through the lower-die intermediate plate12 and the lower-die heat-insulating plate 13. At this point, thetemperature at the lower-die support plate 11, which is heated byenergizing the heaters 15, is suppressed to about 180° C.

Like the lower-die support plate 11, the lower-die intermediate plate 12made of stainless steel (SUS) is formed into the rectangular plate shapewhen viewed from above.

The lower-die heat-insulating plate 13 is constructed by stacking pluralheat-insulating sheets 13 a made of resin materials, such as polyimide(in FIG. 2, the lower-die heat-insulating plate 13 is illustrated whilevertically taken down). Heat-insulating performance of theheat-insulating sheets can be adjusted according to the number ofstacked heat-insulating sheets 13 a. At this point, the lower-dieheat-insulating plate 13 is constructed by the five heat-insulatingsheets, whereby the lower-die transfer plate 14 is adjusted to thetemperature of about 150° C. while the lower-die support plate 11 isheated at the temperature of about 180° C. This prevents a deformationof the resin sheet 25, which is caused by a thermal influence of thelower-die support plate 11. Accordingly, a conveying line for the resinsheet 25 is disposed near the lower die 9, but it is not necessary toincrease a distance in opening the dies, which allows downsizing of thetransfer molding apparatus 2. In closing the dies to heat the resinsheet 25, the lower-die heat-insulating plate 13 plays a role inpreventing a heat loss from the upper die 10 onto the lower die side. Incooling the resin sheet 25, the lower-die heat-insulating plate 13 playsa role in preventing the lower-die support plate 11 from being cooled.

The lower-die transfer plate 14 made of a nickel chrome alloy is formedinto the rectangular plate shape when viewed from above. A transfersurface is formed on an upper surface of the lower-die transfer plate14. In the transfer surface, plural hemispherical small projectingportions having sub-micrometer-scale depths are disposed at arbitraryintervals in an x-axis direction and a y-axis direction. Therefore, theplural hemispherical small recessed portions can be formed on a lowersurface of the resin sheet 25 that is of a transfer destination. Asurface in which the small recessed portions are formed constitutes areflecting surface. The surface functions to reflect light emitted froma light source onto the upper surface side and to output the light. Thesmall projecting portion is not limited to the hemispherical shape, butvarious shapes, such as a triangle in section, may be used as the smallprojecting portion. Not the small projecting portion, but a smallrecessed portion may be formed.

A horizontal surface of the lower die 9 can be moved in the x-axisdirection and the y-axis direction by driving parts (not illustrated),such as a servo motor. A movement amount of the lower die 9 is detectedby a micrometer 16, and a position in the horizontal surface of thelower die 9 can finely be adjusted in the x-axis direction and they-axis direction based on the detection result. The fine adjustment ofthe position in the horizontal surface of the lower die 9 may manuallybe performed using the micrometer 16.

In the upper die 10, an upper-die intermediate plate 18, an upper-dieheat-insulating plate 19, and a retention plate 21 that retains anupper-die transfer plate 20 are sequentially disposed on a lower surfaceof an upper-die support plate 17.

Like the lower-die support plate 11, the upper-die support plate 17 madeof stainless steel (SUS) is formed into the rectangular plate shape whenviewed from above. Plural through-holes are made between the sidesurfaces of the upper-die support plate 17, and heaters 22 andthermocouples (not illustrated) are inserted in the through-holes. Theupper-die support plate 17 can be raised up to the temperature of about280° C. by energizing the heaters 22.

Like the upper-die support plate 17, the upper-die intermediate plate 18made of stainless steel (SUS) is formed into the rectangular plate shapewhen viewed from above.

Like the lower-die heat-insulating plate 13, the upper-dieheat-insulating plate 19 is constructed by stacking pluralheat-insulating sheets 19 a made of resin materials, such as polyimide.At this point, the upper-die heat-insulating plate 19 is constructed bythe two heat-insulating sheets, whereby the upper-die transfer plate 20is adjusted to the temperature of about 240° C. Therefore, the resinsheet 25 can sufficiently be melted when the resin sheet 25 issandwiched between the upper die 10 and the lower die 9.

Like the lower-die transfer plate 14, the upper-die transfer plate 20made of a nickel chrome alloy is formed into the rectangular plate shapewhen viewed from above. As illustrated in FIG. 3, a recess 23 extendedin a width direction is formed in the lower surface of the upper-dietransfer plate 20. The recess 23 is a space surrounded by aperpendicular surface 23 a, a bottom surface 23 b, an inclined surface23 c, and both end faces (not illustrated). Plural arc regions 24 arearrayed in the width direction in the inclined surface 23 c, and manyprojected thread portions each of which has a substantially triangularshape in section are radially extended in a lower half of each arcregion 24.

The recess 23 is configured such that the molten resin sheet 25 flowspartially into the recess 23 to form a thick portion 26 (FIG. 3). Theresin sheet 25 includes an extremely thin film, films having thicknessesof 0.2 to 0.3 mm used in one or more of the embodiments, and filmshaving thickness greater than the thicknesses of 0.2 to 0.3 mm. Thethick portion 26 has a height of a sub-millimeter scale. In one or moreof the embodiments, the thick portion 26 has the height of 0.5 mm. Theprojected thread portion formed in the inclined surface has a projection(surface roughness) of a sub-micrometer scale. In one or more of theembodiments, the projected thread portion has the projection of 0.2 μm.A region where the projected thread portions are formed is also includedin the transfer surface, and the region suppresses the light leakingfrom the inclined surface 23 c by folding the light incident from theplural light sources disposed on the end face side of the thick portion26.

Plural groove portions 27 connecting the recess 23 to the outside areformed in the lower surface of the upper-die transfer plate 20.Although, in one or more embodiments of the present invention, eachgroove portion 27 is formed in the direction (the x-axis direction)orthogonal to the width direction (y-axis direction) in which the recess23 is extended, each groove portion 27 may be formed so as to intersectthe width direction. Therefore, the groove portion 27 can be shortenedto the minimum. Each groove portion 27 is formed so as to be locatedbetween the arc regions 24 and 24. This is attributed to the followingfacts.

As described above, in the upper-die transfer plate 20 of one or more ofthe embodiments, the plural arc regions 24 are arrayed in an inner edgeportion of the recess 23 as illustrated in FIG. 3. Therefore, a flowrate of the molten resin flowing into the recess 23 is uneven when theresin sheet is melted to perform the transfer molding. Morespecifically, as illustrated in FIG. 8 a, in the inner edge portion ofthe recess 23, the flow rate of the molten resin is fast in the arcregion 24, and the flow rate of the molten resin is slow in the regionlocated between the arc regions 24 and 24 adjacent to each other. Aresidual air remaining in the recess 23 of the upper-die transfer plate20 has a substantially even width at pressurization initial andintermediate stages (FIGS. 8B and 8C). However, during thepressurization, a difference in irregularity is increased in the inneredge portion of the residual air due to the uneven flow rate of themolten resin (FIGS. 8D and 8E). In the region located between the arcregions 24 and 24 adjacent to each other, part of the residual air isseparated to become a boundary bubble, and the boundary bubble remainswithout change. In order to equalize the flow rate of the molten resin,the groove portion 27 is provided behind the region where the moltenresin has the slow flow rate. As a result, the residual air can rapidlybe exhausted without generating the boundary bubble in the recess 23.

The groove portion 27 may have a depth greater than or equal to that ofthe recess 23. In one or more of the embodiments, the depth of eachgroove portion 27 is identical to that of the recess 23. The width ofthe groove portion 27 is set to a value such that the bubble does notremain in the recess 23 while an outflow amount of molten-state resin(resin sheet 25) flowing into the recess 23 is suppressed to theminimum.

Thus, when the molten resin flows into the recess 23, the air in therecess 23 can smoothly be guided to the outside by forming the grooveportion 27 connecting the recess 23 to the outside behind the regionlocated between the arc regions 24 and 24. The molten resin flowing intothe recess 23 also partially flows to the groove portion 27. Because thegroove portion 27 has the depth greater than or equal to that of therecess 23, the air does not remain in the region from the recess 23 tothe groove portion 27 (when the groove portion 27 is less than therecess 23 in the depth, a corner portion is formed, and the air possiblyremains in the corner portion). Accordingly, the air does not remain inthe recess 23 and a void is not generated in the thick portion 26.Because an insignificant amount of air remains in the recess 23 even ifthe air remains, a burn is not generated in the molded resin, the aircan be melted in the molten resin by a pressurizing force withoutgenerating the void.

According to knowledge of the inventor, the larger bubble is easilygenerated and remains when the groove portion is narrowed, and the manysmall bubbles are easily generated and remains when the groove portionis widened. Therefore, the width of the groove portion that canefficiently exhaust and remove both the large bubble and the smallbubble was measured. FIG. 6 illustrates a measurement result.

As is clear from FIG. 6, it is found that both the large bubble and thesmall bubble can efficiently be exhausted and removed when the width ofthe groove portion is set to 0.5 mm.

A flow rate ratio of the molten resin, which changes according to thewidth of the groove portion 27, was analyzed. FIGS. 7A and 7B illustratean analysis result.

As illustrated in FIGS. 7A and 7B, in the case that the flow rate ratioof the molten resin is set to 1 for the groove portion 27 having thewidth of zero, the flow rate ratio exceeds 1.2 when the groove portion27 has the width of 0.5 mm, and the flow rate ratio is increased to 1.4when the groove portion 27 has the width of 1.0 mm. Therefore, it isfound that a difference in flow rate between the molten resin in the arcregion 24 and the molten resin in the region located between the arcregions 24 and 24 adjacent to each other is decreased with increasingwidth.

As illustrated in FIGS. 4A and 4B, the groove portion 27 may be extendedso as to stretch into the recess 23 that is used to form the thickportion. As illustrated in FIG. 5, a leading end of the groove portion27 may be extended to the outside of the resin sheet 25 (FIG. 5A), andthe leading end the groove portion 27 may be disposed in the resin sheet25 (FIG. 5B). An accumulating groove portion 27 a (FIG. 5C) in which thebubble is accumulated may be provided at the leading end of the grooveportion 27. The groove portion 27 is not necessarily formed into thegroove shape, but the groove portion 27 may be formed into a widerecessed portion as illustrated in FIG. 5D.

The groove portions 27 are not necessarily disposed at equal intervals,but the groove portions 27 may properly be disposed at differentintervals. The groove portions 27 do not necessarily have the same widthand the same depth, but the groove portions 27 may have afolding-fan-shaped width and depth. A sectional area of a flow path ofthe groove portion 27 may homogeneously increased or decreased, or thesectional area may repeatedly be increased and decreased. The grooveportion 27 is not necessarily formed into a straight shape, but thegroove portion 27 may be curved or meander. The groove portion 27 is notnecessarily parallel to the adjacent groove portion 27, and the grooveportions 27 are not necessarily equal to each other in a length.Particularly, even if the molded product is used as a light guide plate,the extended direction of the groove portion 27 is not necessarilyparallel to the light incident direction. The groove portion may beformed so as to be directly connected to the recess, or the grooveportion may be formed so as to be connected to the recess with at leastanother groove portion interposed therebetween.

In the groove portion 27, the above shapes may be combined as neededbasis.

As illustrated in FIG. 2, the retention plate 21 made of stainless steel(SUS) is formed into the rectangular frame shape, and an opening 28 isformed in the center of the retention plate 21. The upper-die transferplate 20 is retained in the lower surface of the retention plate 21, andexposed upward from the opening 28. The upper surface of the upper-dietransfer plate 20, which is exposed from the opening 28, is irradiatedwith a soft X-ray using a soft X-ray irradiation apparatus 29.Therefore, electricity of the resin sheet 25 is removed, and surroundingdust is prevented from adhering to the resin sheet 25 due to anelectrostatic attraction force. Rods 30 are coupled to both sideportions of the retention plate 21, and the retention plate 21 can belifted and lowered independently of the whole upper die 10 using drivingparts, such as a cylinder (not illustrated).

The whole upper die 10 is lifted and lowered by a press machine 31disposed on the upper surface side of the upper-die support plate 17.The air is supplied to and exhausted from the press machine 31 by an airsupply apparatus 32, and the rod 30 is lifted and lowered to lift andlower the whole upper die 10 with the upper-die support plate 17interposed therebetween.

The resin sheet 25 supplied by the material supply apparatus 1 isconveyed between the upper die 10 and the lower die 9. On an entranceside and an exit side of the die in the middle of the conveying route ofthe resin sheet 25, a support roller 33 that supports the lower surfaceof the resin sheet 25 and a positioning gripper 34 that vertically nipsthe resin sheet 25 are disposed in the order located closer to the diewhile being able to be lifted and lowered. A conveying gripper 35 isdisposed on a downstream side of the conveying route. Like thepositioning gripper 34, the conveying gripper 35 vertically nips theresin sheet 25, and reciprocally moves along the conveying route by adriving part (not illustrated). In the state in which the positioninggripper 34 is opened, the conveying gripper 35 moves onto the downstreamside of the conveying route while nipping the resin sheet 25, whichallows the resin sheet 25 to be conveyed. Behaviors of the supportroller 33 and the grippers are described later.

An air supply duct 36 is disposed on the upper side on the upstream sideof the die, and an exhaust air duct 37 is disposed on the upper side onthe downstream side of the die. The air supplied by a compressor (notillustrated) blows from the air supply duct 36, and the air blows on theresin sheet 25 located between the upper die 10 and the lower die 9 fromobliquely above. The air is sucked from the exhaust air duct 37 by thecompressor (not illustrated), and the air blowing on the resin sheet 25is collected from the air supply duct 36. The air supplied from the airsupply duct 36 is purified, an air flow formed from the air supply duct36 to the exhaust air duct 37 not only cools the resin sheet 25, butalso forms what is called an air barrier to prevent the dust fromadhering to the surface of the resin sheet 25. Because the electricityof the resin sheet 25 is removed by the irradiation of the soft X-ray,the dust does not adhere to the resin sheet 25 due to the electrostaticattraction force.

As illustrated in FIG. 1, adhesive rollers 38 that come into contactwith the upper and lower surfaces of the resin sheet 25 are disposed onthe upstream side of the die. When the adhesive rollers 38 are rotated,the adhesive rollers 38 remove the dust adhering to the surface of theresin sheet 25 while conveying the resin sheet 25.

The film adhesion apparatus 3 causes protective films 39 to adhere tothe upper and lower surfaces of the resin sheet 25 after the transfermolding. The protective film 39 prevents the resin sheet 25 from beingdamaged due to a collision with another member, or prevents the dustfrom adhering to the surface of the resin sheet 25.

The cutting apparatus 4 obtains a half-finished plate 46 by cuttingand/or punching the resin sheet 25 to which the transfer molding isperformed. In the half-finished plate 46, cutting margins are left inthe thick portion 26 and the end face on the opposite side of the thickportion 26.

A cutter is provided on the upstream side, for example, in the materialsupply apparatus 1, and the resin sheet 25 may be cut along theconveying direction in each of the half-finished plates that arepreviously arrayed in the width direction.

The outline machining apparatus 5 includes a jig 40 that positions theplural half-finished plates 46 while the plural half-finished plates 46are stacked and a cutting member 41 that grinds, cuts, and polishes theend face of the half-finished plate 46, namely, the outside surface ofthe thick portion 26 that is positioned by the jig 40.

The plural half-finished plates 46 are stacked in the jig 40, and thejig 40 is disposed while the upper and lower surfaces of the jig 40 arenipped by dummy plates 47. The dummy plates 47 and the half-finishedplates 46, which are disposed while stacked, are retained in the jig 40using a clamp member (not illustrated).

As illustrated in FIG. 9, the cutting member 41 includes a cutting tool41 a and a cutting tool 41 b, which are rotated by driving parts. Thecutting tool 41 a has a drill shapes, and a cutting edge 49 a isprovided at a position, which is point-symmetric in relation to arotating axis, in an outer circumferential surface of the cutting tool41 a. The cutting tool 41 b has a drum shape, and a cutting edge 49 b isprovided at a position that is line-symmetric in relation to a rotatingaxis orthogonal to the rotating axis of the cutting tool 41 a.Therefore, cutting loci of the cutting tools 41 a and 41 b intersecteach other. A specific cutting method performed by the cutting tools 41a and 41 b is described later.

(Behavior)

A behavior of the transfer molding apparatus having the aboveconfiguration will be described below.

(Preparation Process)

As illustrated in FIG. 1, the upper die 10 is lifted to open the die,and the leading end portion of the resin sheet 25 supplied from thematerial supply apparatus 1 is nipped by the conveying gripper 35 (FIG.2). After the conveying gripper 35 is moved, the resin sheet 25 isnipped by the positioning grippers 34 and 34 to dispose the resin sheet25 in a region where the upper die 10 and the lower die 9 face eachother (conveying process).

The die is previously heated by energizing the heater 15. As describedabove, because the heat-insulating plate is interposed, the upper-dietransfer plate 20 becomes about 240° C. in the upper die 10, and thelower-die transfer plate 14 becomes about 150° C. in the lower die 9. Inthe lower die 9 located near the resin sheet 25, the upper surface ofthe lower die 9 is suppressed to around a glass-transition temperature,and the resin sheet 25 is bent downward by a thermal influence.Therefore, a trouble such that the resin sheet 25 comes into contactwith the lower-die transfer plate 14 is not generated (preheatingprocess).

(Transfer Molding Process)

The support roller 33 and the positioning gripper 34 are lowered toplace the resin sheet 25 on the lower-die transfer plate 14 of the lowerdie 9. The press machine 31 is driven to lower the upper die 10, and thetransfer surface of the upper-die transfer plate 20 is abutted on theresin sheet 25. At this point, a pressure acting on the press machine 31is suppressed to a low level, and the resin sheet 25 is lightly nippedbetween the dies. Therefore, the resin sheet 25 is heated to remove amoisture included in a surface layer (preheating process).

A pressurizing force of the press machine 31 is increased when apreviously-set time (a first setting time) elapses since the preheatingprocess is started. As described above, the resin sheet 25 is made ofpolycarbonate (melting points of 220 to 230° C., and a glass-transitiontemperature of about 150° C.). Because the upper-die transfer plate 20is heated to 240° C., the temperature of the resin sheet 25 exceeds themelting point, and the resin sheet 25 becomes the molten state. In thelower die 9, although the lower-die transfer plate 14 has thetemperature of 180° C., the heat is not lost from the lower die sidebecause the lower-die heat-insulating plate 13 is disposed. Therefore,the whole region of the resin sheet 25 nipped by the dies exceeds themelting point to become the molten state (heating and pressurizationprocess).

The pressurizing force of the press machine 31 is applied from the upperdie 10. Therefore, the resin sheet 25 is thinned in the portion nippedby the dies, and part (an upper surface portion) of the resin sheet 25flows into the recess 23 formed in the upper-die transfer plate 20. Whenthe molten resin flow into the recess 23, the residual air in the recess23 is exhausted to the outside through the groove portion 27. The recess23 is completely filled with the molten resin, and part of the moltenresin flows out to the groove portion 27. The depth of the grooveportion 27 is greater than or equal to the depth of the recess 23 (inthis case, the same depth). Therefore, the air does not remain in therecess 23, but the air is smoothly exhausted to the outside. Troubles,such as the burn, are not generated because the residual air is notcompressed in the recess 23. Even if a small amount of air remains inthe recess 23, because the sufficient pressurizing force is applied tothe recess 23, the air can be melted in the molten resin withoutgenerating the void.

The upper die 10 is lifted when a previously-set time (a second settingtime) elapses since the heating and pressurization process is started.However, the upper-die transfer plate 20 remains abutted on the resinsheet 25 by driving the cylinder. At this point, the air is suppliedonto the upper-die transfer plate 20 through the air supply duct 36. Theheated upper-die support plate 17 is distant from the resin sheet 25,and the air blows onto the upper-die transfer plate 20 from the airsupply duct 36. That is, the resin sheet 25 can be cooled only throughthe upper-die transfer plate 20. The heat of the upper-die support plate17 does not affect the cooling of the resin sheet 25, so that the resinsheet 25 can effectively be cooled in a short time. That is, the resinsheet 25 can be cooled in a short time to temperatures of 150° C., whichis of the glass-transition temperature of polycarbonate, or less. Inthis case, because the upper-die support plate 17 and the upper-dieintermediate plate 18 are not cooled, an energy loss is decreased, andthe next transfer molding process can smoothly be started in a shorttime (cooling process).

When a previously-set time (a third setting time) elapses since thecooling process is started, namely, when the molten resin is solidifiedto stabilize the shape by the cooling, the upper-die transfer plate 20is lifted and released from the molded portion. The support roller 33 islifted to release the molded portion from the lower-die transfer plate14. Therefore, the thick portion 26 having the sub-millimeter-scaleheight, namely, the height of 0.2 mm is formed on the upper surface ofthe resin sheet 25. The plural projected thread portions having thesub-micrometer-scale saw-tooth shape, namely, the 14-μm saw-tooth shapeare formed on the inclined surface of the thick portion 26. On the otherhand, on the lower surface of the resin sheet 25, the pluralhemispherical small recessed portions are formed at constant intervalsin the x-axis direction and the y-axis direction (die releasingprocess).

Conventionally, although the sub-micrometer-scale projection can beformed in the resin sheet 25 by the transfer molding, thesub-millimeter-scale thick portion 26 cannot simultaneously be formed.The use of the transfer molding apparatus 2 having the die structure cansimultaneously form the sub-micrometer-scale projected thread portionand the sub-millimeter-scale thick portion 26 in the resin sheet 25.Because the whole resin sheet 25 nipped between the dies is melted inthe transfer molding, the internal stress does not remain in thehalf-finished plate 46 obtained by the solidification of the meltedresin sheet 25. Accordingly, the plural LEDs are disposed on the endface side of the thick portion 26, and the whole upper surface exceptthe thick portion 26 can evenly be irradiated with the light withoutdeviation after the light is transmitted through the thick portion 26.

(Film Adhesion Process)

The resin sheet 25 to which the transfer molding is performed by thetransfer molding apparatus 2 is further conveyed onto the downstreamside, and the film adhesion apparatus 3 causes the protective films 39to adhere to the upper and lower surfaces of the resin sheet 25. Theprotective film 39 prevents the resin sheet 25 from being damaged due tothe collision with another member, or prevents the generation of thetrouble due to the surrounding dust adhering to the half-finished plate46. The half-finished plate 46 becomes the light guide plate that is oneof the optical members through the subsequent processing. Then theprotective film 39 is peeled off from the resin sheet 25 when the liquidcrystal panel is assembled.

(Cutting Process)

The resin sheet 25 in which the protective films 39 adhere to the upperand lower surfaces is further conveyed onto the downstream side, thecutting apparatus 4 cuts the resin sheet 25 in units of half-finishedplates in the conveying direction to form a reed-shaped resin sheet 25.Then the resin sheet 25 is punched in each half-finished plate 46. Atthis point, the half-finished plate 46 has the cutting margins for anouter shape machining process in the thick portion 26 and the end faceon the opposite side of the thick portion 26, and a cutting backclearance portion 46 a is properly formed in a corner portion of thehalf-finished plate 46.

(Outer Shape Machining Process)

As illustrated in FIG. 9A, the half-finished plates 46 obtained throughthe cutting process are stacked such that the thick portions 26 arealternately located on the opposite sides. At this point, one end faceand one side surface of the stacked half-finished plates 46 and dummyplates 47 are abutted on and positioned in two side surfaces (notillustrated) orthogonal to each other in the jig 40, and fixed.

After roughly cut using the drill-shaped cutting tool 41 a of thecutting member 41, the stacked half-finished plates 46 and dummy plates47 are polished as finish cutting using the drum-shaped cutting tool 41b.

The half-finished plates 46 and dummy plates 47, which are fixed to thejig 40, are slid to cut the end faces of the half-finished plates 46 anddummy plates 47, which are projected from the side surface of the jig40, using the cutting tool 41 a (FIG. 9B). Because by the cutting withthe cutting tool 41 a the cutting edge 49 a of the cutting tool 41 areaches the cutting back clearance portion 46 a immediately before thecutting is ended, advantageously a burr of the cutting is not generated(FIG. 9C). Accordingly, part of the cutting back clearance portion maybe left after the cutting.

The projections of the half-finished plates 46 and dummy plates 47 aregreater than or equal to a minimum length (the cutting margin) in whichthe jig 40 and a clamp plate 45 are not cut using the cutting tools 41 aand 41 b, and is less than or equal to a maximum length in which theburr caused by a flutter is not generated during the cutting. Thecutting back clearance portion 46 a having a predetermined angle (inthis case, 3° to 10°) with respect to the end face to be cut is formedin the corner portion of the cutting surface of each half-finished plate46. The cutting back clearance portion 46 a may be a tapered surface oran R-surface. In the case that the cutting back clearance portion 46 ais the tapered surface, the tapered surface may have angles of 3 degreesto 10 degrees. When the angle of the tapered surface is less than 3degrees, the tapered surface is hardly punched, and desired punchingaccuracy is hardly obtained. When the angle of the tapered surface isgreater than 10 degrees, the light is unintentionally reflected toadversely affect the optical performance.

Then the half-finished plates 46 and dummy plates 47, which are fixed tothe jig 40, are slid toward the cutting tool 41 b to cut the end facesof the half-finished plates 46 and dummy plates 47, which are projectedfrom the side surface of the jig 40, from above using the cutting edge49 b of the cutting tool 41 b.

In one or more of the embodiments, because the loci of the cutting edges49 a and 49 b of the cutting tools 41 a and 41 b intersect each other,advantageously the polishing can efficiently and cleanly be performed.

In the case that one end face of the stacked half-finished plates 46 anddummy plates 47 is finished using the cutting tool 41 b, the burr islocated in the dummy plate 47 even if the burr is formed, but the burris not formed in the half-finished plate 46.

After one end of the half-finished plates 46 and dummy plates 47 is cut,the clamp state of the jig 40 is released, and the other end of thehalf-finished plates 46 and dummy plates 47 is cut in the similar mannerwhile projected from the side surface of the jig 40. Therefore, plurallight guide plates 48 are completed at one time.

For example, as illustrated in FIG. 10, the completed light guide plate48 includes a thick portion 48 a having the thickness of 0.5 mm and athin portion 48 b having the thickness of 0.2 mm, the thick portion 48 ahas a substantially trapezoidal shape in section, and the projectedthread portion is provided in a lower half of the inclined surface ofthe thick portion 48 a. Many small recessed portions are formed in thebottom surface of the light guide plate 48.

A diffuser plate 52, a prism sheet 53, and a liquid crystal panel 54 aresequentially stacked on the light guide plate 48 placed on a base 51. AnLED 55 that is of the light source is disposed in a lateral portion of aperpendicular surface of the thick portion 48 a to obtain a liquidcrystal display device 50.

Therefore, the light emitted from the LED 55 is guided to the thinportion 48 b without leaking to the outside because of the projectedthread portion of the thick portion 48 a, and evenly diffused by thehemispherical small recessed portion in the bottom surface, and theliquid crystal panel 54 is irradiated with the light through thediffuser plate 52 and the prism sheet 53.

The area light source device may solely be used without providing theliquid crystal panel 54.

The present invention is not limited to the above embodiments, butvarious changes can be made.

For example, in one or more of the embodiments, the resin sheet 25 ismelted and part of the molten resin is caused to flow into the recess 23formed in the upper-die transfer plate 20, thereby forming the thickportion 26 in FIG. 3. Alternatively, the thick portion 26 may be formedas follows.

The resin sheet 25 is not melted and part of the molten resin is notcaused to flow into the recess, but an additional member (for example, aresin piece) may be supplied according to the recess 23 of the upper-dietransfer plate 20. Therefore, the thick portion 26 can easily be formed.

The additional member may integrally be formed by previously thickeningpart of the resin sheet 25. Therefore, a mechanism that supplies theadditional member is eliminated to improve workability.

In one or more of the embodiments, the recess is provided in the edgeportion on one side of the upper-die transfer plate 20. Alternatively,the recess may be provided in a central portion of the upper-dietransfer plate 20, the lower-die transfer plate 14, or both theupper-die transfer plate 20 and the lower-die transfer plate 14.

The die structure including the upper die 10 and the lower die 9 is usedin one or more of the embodiments. Alternatively, a die that ishorizontally opened and closed may be used.

In one or more of the embodiments, the transfer surfaces are formed inthe upper-die transfer plate 20 and the lower-die transfer plate 14.Alternatively, the transfer surface may be formed in one of theupper-die transfer plate 20 and the lower-die transfer plate 14. Thetransfer plates are eliminated, and the transfer surfaces may directlybe formed in the dies (for example, an intermediate plate).

In one or more of the embodiments, the whole upper-die transfer plate 20is evenly heated. However, the whole upper-die transfer plate 20 is notnecessarily evenly heated. For example, the neighborhood of the recessmay intensitively be heated. Therefore, the good molten state of theresin can be obtained in the recess to form the good thick portion 26 inwhich a shrinkage is not generated.

In one or more of the embodiments, the resin sheet 25 is heated andpressurized while nipped between the upper-die transfer plate 20 and thelower-die transfer plate 14, and the whole resin sheet 25 is melted.Therefore, according to one or more embodiments of the presentinvention, in at least one of the transfer plates 20 and 14, a flowregulating structure that regulates the flow of the molten resin isprovided in a rim portion.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

1. A die structure comprising: a first die; a second die configured tobe separated from and brought into contact with the first die; and atransfer member disposed in at least one of the first and second dies,wherein the transfer member performs transfer molding while bringing atransfer surface into contact with a resin sheet supplied between thefirst and second dies, and wherein the transfer member includes a recessthat is formed in the transfer surface and at least one groove portionthat is connected to the recess.
 2. The die structure according to claim1, wherein the at least one groove portion has a depth greater than orequal to that of the recess.
 3. The die structure according to claim 1,wherein the at least one groove portion is connected to an outside ofthe transfer member.
 4. The die structure according to claim 1, whereinthe at least one groove portion is formed to intersect the recess formedin the transfer surface.
 5. The die structure according to claim 1,wherein the transfer member includes an auxiliary groove portion that isformed to be connected to the recess, and wherein the at least onegroove portion is connected to the recess through the auxiliary grooveportion.
 6. The die structure according to claim 1, wherein each grooveportion has a sectional area of a folding-fan-shaped flow path in whicha pressure of a molten resin flowing from the recess is substantiallyequalized.
 7. The die structure according to claim 1, wherein eachgroove portion is disposed in a position where a flow rate of the moltenresin is substantially equalized.
 8. A transfer molding apparatuscomprising the die structure according to claim
 1. 9. A transfer moldingmethod comprising: an insertion step of inserting a resin sheet betweena first die and a second die, which are disposed opposite each other; asandwiching step of sandwiching the resin sheet between the first andsecond dies while a transfer surface of a transfer member is broughtinto contact with at least one of surfaces of the resin sheet; and atransfer molding step of heating at least one of the first and seconddies to melt at least a surface portion of the resin sheet with whichthe transfer surface of the transfer member is brought into contact, andexhausting residual air remaining in a recess through a groove portionconnected to the recess when a thick portion is formed by the recessformed in the transfer surface.
 10. The transfer molding methodaccording to claim 9, wherein the groove portion has a depth greaterthan or equal to that of the recess.
 11. The transfer molding methodaccording to claim 9, wherein a molten resin is caused to flow partiallyto the groove portion in which a nonproductive portion is molded in thetransfer molding step.
 12. An optical member comprising: a resin memberformed by: inserting a resin sheet between a first die and a second die,which are disposed opposite each other, sandwiching the resin sheetbetween the first and second dies while a transfer surface of a transfermember is brought into contact with at least one of surfaces of theresin sheet, heating at least one of the first and second dies to meltat least a surface portion of the resin sheet with which the transfersurface of the transfer member is brought into contact, and exhaustingresidual air remaining in a recess through a groove portion connected tothe recess when a thick portion is formed by the recess formed in thetransfer surface.
 13. An area light source device comprising: theoptical member according to claim 12; and a light source that isdisposed in at least one end face of the optical member, wherein lightincident from the light source to the optical member is output through alight exit surface of the optical member.
 14. A liquid crystal displaydevice comprising: the area light source device according to claim 13;and a liquid crystal panel.
 15. A mobile device comprising the arealight source device according to claim
 13. 16. The die structureaccording to claim 2, wherein the at least one groove portion isconnected to an outside of the transfer member.
 17. The die structureaccording to claim 2, wherein the at least one groove portion is formedto intersect the recess formed in the transfer surface.
 18. The diestructure according to claim 3, wherein the at least one groove portionis formed to intersect the recess formed in the transfer surface. 19.The die structure according to claim 2, wherein the transfer memberincludes an auxiliary groove portion that is formed to be connected tothe recess, and wherein the at least one groove portion is connected tothe recess through the auxiliary groove portion.
 20. The die structureaccording to claim 3, wherein the transfer member includes an auxiliarygroove portion that is formed to be connected to the recess, and whereinthe at least one groove portion is connected to the recess through theauxiliary groove portion.